1. Field of the Invention
This invention relates generally to materials handling, and more particularly to unloading dry bulk materials from the holds of ships.
2. Description of the Prior Art
Increasing concern over the environment has spurred numerous laws regulating the manner and extent to which industrial processes may affect the environment. Particularly with regard to materials handling apparatus and processes, this has meant tighter restrictions on the amount of material which can be released into the atmosphere. Efficiently meeting, and better still exceeding, these standards has been especially difficult in the maritime setting where dry bulk materials must be unloaded from the holds of ships. Processes and apparatus which might work well on shore are often too expensive or unworkable in the maritime setting.
The transitory nature of the cargo ships at the dock makes it difficult to use bulk transfer processes and apparatus which are successful on land. In some cases it would be necessary to modify each and every ship to accomodate a particular new process. In other cases it might be necessary to modify the process to accomodate different ship designs. The huge amounts of material which are moved can also be a significant impediment. It is not uncommon for each hold of a ship handling cement, for example, to carry eleven thousand tons of the material. Many processes which might otherwise be suitable are not capable of handling large quantities of materials such as this.
Bulk materials handling in the maritime setting is almost always an open-air process. Each ship hold is unloaded through an opened main hatch in the deck of the ship. Conveyors, conduits and the like necessary for continuous unloading processes are set down into, and extend out from, the hold through the opened main hatch. In the event of a rainstorm, sudden winds or the like, the hatch cannot be easily closed. If the bulk material can be damaged by water, as with cement, extensive damage can result.
Materials handling is an old and varied art. Hoppers, conveyors, buckets, conduits and the like, of many shapes and sizes, have been used to move bulk materials from one place to another. This equipment, however, often does not meet often newer and stricter environmental standards when used in conventional processes. It would desirable to provide a process and apparatus which would move bulk materials from the holds of ships to on-shore collection stations in a manner which meets or even exceeds environmental standards. It would also be desirable if the system would operate on many ship designs and with no modification necessary to existing ships. The crews on ships are typically responsible for unloading. It would therefore be desirable if the process of unloading did not require the extensive development of new skills such that crews uneducated in the workings of the process and apparatus would have difficulty in unloading the cargo.